Alloy Head Verses ALL Iron or Alloy Engine

You dont think motor companies pay thousands of engineers every week to overlook what dissimilar metals do when under heat cold cycles do you?

Current Nissan 4.2 TD is all cast Iron.... Warms up quickly but even after sitting for 4 hours when you start it again is still warm....

3.0L is alloy head and cast iron block

Alloy head reeks of compromise, like they couldn't afford to build the whole thing in alloy... what are the advantages of alloy head over all alloy?

1kz-TE 3.0LTD Toyota's in prado and surf are alloy head an cast block. Mitsubishi is Alloy/Alloy.
If you go to: www.carsales.com.au and select car research it will tell you to constrution of head vs block on most current and past models.

Getting a matched head and block are still no garantees of saving a cracked head. The Toyota 2h motor was tough as teak but overheat them and the heads will crack like glass, The commodore 3l is another example as far as I can tell the failure rates of the heads between 150-200k was extremely high probably over 50%. The local spare parts guys keep changeover 1hz heads on display coz they go fairly easily too if you cant see your temp gauge. Bottom line is probably the best way to keep your head is to watch the temp gauge no matter what the construction material make or model

If you are going to base your purchase decision on what the engine/head is made out of I think you might be overlooking a few things.

Bjorn asked:
How much easier Is it to crack an Alloy head on an iron block compared to an all alloy or all iron construction?

It's 4.3257% easier! As shown by numerous university tests...

But seriously folks, if you don't want to crack the head on your engine, keep it full of coolant and don't overheat it, pretty simple really.

cheers

Alloy heads, well I have not had a good run out of them. My Suby overheated and result was a cracked head, virtually straight away. My 1KZ-TE in my Surf (same motor as Prado) overheated 6 months ago and now 6 months later the aparant heating stress, warping or whate ver has resulted in a cracked head. The cast iron is bullet proof and I am reluctant to get another alloy head. Well if I do I will have an alarm fitted to the temp sensor to ensure the engine does not get near over heating (I'll get the alarm to sound when it hits 3/4 way).

I remember limping home in my old Ford escort with a bung radiator. Driving down from Noosa to Brisbane, in sections of 500m at no more than 60km hour! Took a good 5mins between sections to cool the car down, and many hours to get home! The temperature gauge was like a yo-yo, and the car lived to fight another few years.

The joy of uni days and no cash for a towtruck!

Cheers,

Glenn.

Ford Falcons have had a alloy head/cast block problem for years, head gaskets are a real problem.

For my money go with all cast configuration, it'll be safer in the long run.